CVE-2026-107297
Received Received - Intake

msgpack5 Streaming Decoder Quadratic CPU Consumption Vulnerability

Publication date: 2026-10-08

Last updated on: 2026-10-08

Assigner: GitHub, Inc.

Description
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. This issue is fixed in version 6.1.0.

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Meta Information

Published
2026-10-08
Last Modified
2026-10-08
Generated
2026-10-08
AI Q&A
2026-10-08
EPSS Evaluated
N/A
NVD
CVE-2026-107297
EUVD
EUVD-2026-95108

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
mcollina msgpack5 < 6.1.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-407 An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

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Executive Summary

msgpack5 is a MessagePack v5 library for Node.js and browsers. A flaw exists in versions before 6.1.0 where the streaming decoder incorrectly handles incomplete arrays or maps. When data is split into small chunks, the decoder repeatedly reprocesses valid elements, causing excessive CPU usage and event loop blocking.

Detection Guidance

This vulnerability can be detected by monitoring CPU usage spikes during MessagePack data processing. Check for repeated decoding of the same data chunks in msgpack5 versions prior to 6.1.0. Use tools like top, htop, or perf to observe CPU consumption during message parsing.

Impact Analysis

This vulnerability can lead to high CPU consumption and event loop delays, potentially causing application slowdowns or crashes. Attackers could exploit it to degrade performance or disrupt services by sending specially crafted MessagePack data.

Compliance Impact

This vulnerability primarily impacts system availability due to high CPU usage caused by quadratic parsing of MessagePack data. While it does not directly expose or leak data, prolonged CPU exhaustion could disrupt services handling sensitive information, potentially affecting compliance with availability requirements in GDPR and HIPAA.

Mitigation Strategies

Upgrade msgpack5 to version 6.1.0 or later immediately. If upgrading is not possible, implement strict input validation to limit chunk sizes and prevent malicious splitting of MessagePack containers. Monitor network traffic for unusually small, frequent chunks.

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